The present invention relates to a wireless communication system capable of a broad band package data transmission between mobile terminal stations carried by vehicles and fixed base stations fixedly provided along a traveling route of the vehicles, for example, between vehicles and a roadside.
As a wireless communication technology in the field of mobile communication, cellular communication systems such as PDC (Personal Digital Cellular) have already been realized. In PDC, service area is divided into a lot of wide radio wave zone referred to as a cell which is a macro cell having a radii of 0.5 km-20 km, and a fixed radio base station (BS) is installed in the center of each cell as shown in FIG. 15A. Due to the macro cell structure, only a small number of base stations are required in comparison with the micro cell having a radii of 0.1 km-0.5 km for PHS (Personal Handy-phone System). Thus, the infrastructure cost is improved. In addition, each cell has a part overlapping with adjacent cells to realize continuous type communication. Because of this, the terminal station (mobile station) can carry out communications without interruption.
However, since each cell has a part overlapping with adjacent cells as shown in FIGS. 15A and 15C, it is required to change the carrier frequency to be different from those of the adjacent cells to prevent radio interference. Therefore, the whole frequency ranges (810 MHZ-826 MHz, 1429 MHz-1453 MHz) given to service (PDC) is required to be divided and allocated to each cell. Specifically, the carrier frequency is divided into seven frequencies f1-f7 as shown in FIG. 15A. The frequency band which individual user can use becomes narrow in comparison with the whole band. As a result, the transmissible data rate decreases.
Moreover, since each cell is allocated relatively wide area, multiple access is adopted to cope with the situation wherein a plurality of users— mobile terminals exist in the cell. This results in need for the division of access time to be allocated to each user, for instance, Time Division Multiple Access (TDMA) shown in FIG. 15B, Frequency Division Multiple Access (FDMA), or Code Division Multiple Access (CDMA). As a result, the average data transmission rate decreases.
Thus, the application of a cellular communication system to the communication between the a vehicle and a roadside causes a decrease of communication resources such as time and frequency allocated to each user so that the realization of broad band data transmission becomes difficult.